Introduction of Magnets

Presented by:Challa. Vyshnavi Reddy,

6th ClassD/O Madhava ReddyKeshava Reddy School-Kandi, SANGAREDDY,TELANGANA, INDIA

MAGNET

An object which attracts magnetic substances.

Ex- Steel, Cobalt, Iron etc

How magnet was found?

In Asia there is a place called magnesia. There lived a sheep herder. Once he took his sheep's and went for a walk then he sat at a stone he had a wooden stick and at end there is an iron cap. As he sat on the stone he was going the stick is attached to the stone. Then he founded the magnet.

Different Types Of Magnet

Names of magnets

Bar Magnet

Ring Magnet

Horse Shoe Magnet

Cylinder Magnet

Ball Ended Magnet

SUBSTANCES

MAGNETIC SUBSTANCES

• Ex- steel, cobalt, iron etc

NON-MAGNETIC SUBSTANCES

• Ex- wood, plastic, paper etc

MAGNETIC SUBSTANCE

Substance which attracts to magnet

MAGNETIC SUBSTANCES

FERRO MAGNETIC STUBSTANCES

• The substances which attracts to magnet strongly

PARA MAGNETIC SUBSTANCES

• The substances which attracts to magnet weakly

DIA MAGNETIC SUBSTANCES

• The substances which repels to the magnet

FERRO MAGNETIC SUBSTANCES Ex: steel, iron , cobalt, nickel etc

PARA MAGNETIC SUBSTANCES Ex: aluminum , chromium ,

manganese etcDIA MAGNETIC SUBSTANCES Ex: gold, mercury, water, silver

etc

NON-MAGNETIC SUBSTANCE

Substances which can’t attracted by magnet

PROPERTIES OF MAGNET

Attractive Property

Navigation Property

Same Attraction Opposite

Repel

Opposite Attraction Same

Repel

LAWS OF MAGNET LIKE poles not attract

each other UNLIKE poles attract

each other

ATTRACTIVE PROPERTY Magnet has a property to

attract the magnetic substances

NAVIGATION PROPERTY Magnet also has a property

to show the direction

Opposite Attraction And Same Repel

Unlike poles:The poles are unlike they will attract to each other

Same Attraction Opposite Repel

Like poles:The poles are like they will not attract to each other.

TWO POLES OF A MAGNET

As magnet has poles like which earth has

IN CHINA THERE IS A STORY

In china there is a sea in this sea there is a black stone. When people goes towards sea the ship dashed to this stone and collapse the ship. Then they found the magnet. They also named this stone as lode or lead stone.

To Know the Direction with Magnet

When the sharp end of a magnet

shows the north pole. Chinese

have been invented as the stone

always collapse the ships of

people who goes into the sea. So

they al so saw the directions of

magnet. As the base at south

POLES:

1. Geometric PolesThe extreme ends of the poles

2. Magnetic Poles

The inside poles of magnet

End Points

MAGNETIC AXIS

The horizontal line drawn from north pole to south pole

EQULATERAL LINE

The vertical line perpendicular drawn to divide north pole and south pole

MAGNETIC LENGTH The distance between north

pole to south pole

GEOMETRIC LENGTH

The distance between two geometric poles

Magnetic North And South Poles

Take a magnet and inflate it. The sharp point of magnet goes to geometric north pole called magnetic north pole and the base of the magnet shows the geometric south pole called magnetic south pole.

RELATION BETWEEN MAGNETIC AND GEOMETRIC LENGTH

Magnetic length =5/6 x geometric length EXAMPLE 1. AB =12cm, NS =? 5\6 X 12 NS=10

Methods To Make An Artificial Magnet

Single Touch Method

Double Touch Method

Electrical Method

SINGLE TOUCH METHODPlace a steel bar on a table. Place a magnet and one end of its pole is placed .Stroke the magnet from one end to another end of a steel bar and lift the magnet and place again from where it starts and repeat the process.

DOUBLE TOUCH METHOD

Place a steel bar and place two magnets on the steel bar at the center of the bar. Stroke the magnets to the opposite sides of the magnets. Repeat the same process

ELECTRICAL METHODInsulated copper wire is wound on a nail the ends of the copper wire connected to the battery. In the battery the dry cells are places in +ve and –ve terminals in series.

To prove these artificial magnets have the attractive property

Take some iron nails and keep near to the bars if the iron nails attract then we can prove that they are artificial magnet

TEMPORARY MAGNETS The attractive property in a

magnet is not permanent

PERMANENT MAGNETS They remains the attractive

property of a magnet

DE MAGNETIC INDUCTION Process of losing the attractive

property of magnet Ex: By Heating , Hardly Handling,

Throwing etc.

MAGNETIC INDUCTION

Take a magnet and a iron nail another nail attracts to the first nail because the attractive property gains to the nail.

Magnetic field

The attractive lines of a magnet

TO KNOW THE MAGNETIC FIELD:

Take a magnet and keep a

paper on a magnet and keep some iron nails on a paper and gently move the paper then the iron nails comes to the shape of the magnetic fields.

EXPERIMENT:

PROPERTIES OF MAGNETIC LINES

North to south pole around magnet

Direction of magnetic field

They don’t intersect each other

Density of magnet gives the

intensity of magnetic field

NORTH AND SOUTH POLE AROUND MAGNET

The magnetic field around goes from north pole to south pole from out but inside south pole to north pole.

Direction of Magnetic Field

IF we draw a straight line from any line from a Magnetic Field it is Called Tangent

They doesn't intersect each other

If the magnetic lines intersect there will be 2 directions but it should has only 1 directions

Density of magnet gives intensity of magnetic field

When lines are more then intensity is more. If lines are less intensity is less

MAGNETIC KEEPERS When magnets exposed to air it

starts demagnetize so keep 2 soft iron pieces so if the attractive property looses it goes to the iron pieces

POLE STRENGTH

The ability of attractive property of a magnet

MAGNETIC MOMENT

The Product Of Pole Strength And Magnetic Length

Formula

M x length of magnet M = m x 2L M = a .

m x m

= Am2

UNITS

UNIT OF POLE STRENGTH IS AMPEAR METER =Am UNIT OF MAGNETIC MOMENT IS AMPEAR

METER SQUARE =Am2

Inverse Square Law of Magnetism

Take 2 magnets and place them on a table so now the

distance of the monopoles of magnet is considered as ‘d’

and the attraction or repulsion is force the product of pole

strength is m1m2.Delivation is F is inversely proportional

to the product of pole strength that is F∞ m1m2. As the

force is directly proportional to square distance between

the distance of the monopoles of magnet that is F∞1\d2 .

Then F∞m1m2 \d2 we should not use proportional symbol

we should a constant so we use K because it is a

proportionality constant then F=km1m2\d2 . As k=10-7.